The present invention relates to conveyor systems, and more particularly, to a star and guide conveyor system.
Star and guide conveyor systems have long been used in the packaging industry to convey containers from one location to another. Typically, star and guide conveyor systems are used to transfer containers into and out of rotary style filling and capping machines. A conventional star and guide conveyor includes a pair of star wheel assemblies positioned on opposite sides of a centerguide assembly. Each star wheel assembly includes top and bottom star wheels that are spaced apart to separately engage top and bottom portions of the container. The periphery of each star wheel is shaped to form a number of evenly spaced transfer pockets that scoop containers into the star and guide conveyor system one at a time as the wheel rotates. The centerguide assembly is located between the two star wheels and has a somewhat hour-glass shape that follows a portion of the periphery of both wheels. The centerguide assembly includes top and bottom guides that are positioned adjacent to the top and bottom wheels. The centerguide assembly is spaced apart from the star wheel assemblies to define a corridor of the appropriate width to hold the containers in the transfer pockets.
In a conventional arrangement, a timing conveyor, such as a timing auger, delivers containers to the star and guide conveyor along a path substantially tangent to the star wheel. The transfer pockets of the first rotating star wheel assembly sequentially engage the spaced apart containers to draw them into the star and guide conveyor. As the assembly rotates, the container is conveyed around a portion of the periphery of the wheels through the corridor defined between the wheels and the centerguide assembly. The centerguide assembly holds the container in the transfer pockets as it moves through the corridor. When the container exits the corridor, continued rotation of the star wheel assembly causes the container to pass out of the transfer pockets onto the rotary table or packaging machine. The containers are filled, capped, or otherwise processed as they are moved to the discharge end of the packaging machine. The second star wheel assembly is located adjacent to the discharge end of the packaging machine to take the containers from the packaging machine. The transfer pockets of the second rotating star wheel assembly sequentially engage the containers to support and guide them as they disengage the filler nozzle or capper chuck. The star wheel assembly proceeds to convey the containers around a portion of the periphery of the wheels through the corridor defined by the centerguide assembly and second star wheel assembly. Again, the centerguide assembly holds each container in the transfer pockets until the appropriate time for it to be released to an outfeed conveyor.
The geometry of the transfer pocket and its spacing from the centerguide determine which size and shape container can be conveyed by a particular set of stars and guides. For example, containers having a larger cross sectional area require larger transfer pockets and a larger corridor between the wheels and centerguide, while containers having a small cross sectional area require smaller pockets and a smaller corridor.
One method for switching between different size containers is to provide interchangeable sets of star wheels and centerguides. The various star wheels have different size and shape transfer pockets each specifically designed to convey a specific container. In addition, the various centerguides are dimensioned to provide the appropriate corridor width for a specific container. Each time the star wheels and centerguide are converted, the system must be re-timed to correspond to the movement of the timing conveyor, packaging machine and outfeed conveyor. Changeover is labor intensive and time consuming.
To overcome the problems associated with changeover, star wheels have been provided with spring-biased arms located in each of the transfer pockets. The spring-biased arms pivot from the leading edge of each transfer pocket backward toward the trailing edge. As a result, the arm engages the sidewall of the container forcing it backward against the trailing end of the transfer pocket allowing a single star wheel to accommodate various size containers.
However, when the spring-biased arm forces the container backward in the transfer pocket, it also shifts the filler neck of the container backward. This backward shift of the container throws off the timing of the system causing the neck opening of smaller containers to arrive at the filling or capping station later in the packaging machine's timing cycle. Timing errors can result in drips, spills, broken filler nozzles, and crossthreaded or uncapped containers.
In addition, smaller size containers are inadequately supported when they are transferred through the corridor between the star wheel assemblies and the centerguide assembly. The fixed spacing between the star wheels and centerguide assembly is designed to accommodate the largest diameter container accepted by the star wheels. As a result, when smaller sized containers are conveyed through the corridor they do not contact the centerguide assembly. Because the container is not supported on both sides, it may float out of the transfer pockets or even tip over spilling the contents and potentially blocking the corridor.
In an attempt to overcome the problems associated with a fixed width corridor, the centerguide assembly has been provided with a spring-biased arm pivotally attached to the centerguide at the trailing end of the corridor. The spring-biased arm contacts the sidewall of the container urging it backward in the transfer pockets to ensure that the container is properly aligned as it reaches the packaging machine. The spring-biased arm only contacts the container at the end of the corridor. As a result, the container is free to float or tip throughout most of the corridor.